Magnesium structures for storing and purifying aralkyl halides



United States Patent 3,405,039 MAGNESIUM STRUCTURES FOR STORING ANDPURIFYING ARALKYL HALIDES Charles F. Raley, Jr., Midland, Mich.,assignor to The Dow Chemical Company, Midland, Mich., a corporation ofDelaware Filed Aug. 9, 1965, Ser. No. 478,455

3 Claims. (Cl. 20386) ABSTRACT OF THE DISCLOSURE Method for handling andpurification of chlorinated hydrocarbons such as methyl chloride, carbontetrachloride, methyl chloroform, benzyl chloride, ethylbenzyl chloride,chloroethylbenzyl chloride or vinylbenzyl chloride consisting ofconducting such acts in magnesium alloys which contain alloyingingredients of 09% by weight of aluminum, and up to 6% of at least oneof manganese, thorium, zinc and zirconium.

The present invention relates to novel methods for handling chlorinatedhydrocarbons. More particularly the present-invention concerns thestorage of chlorinated hydrocarbons such as methyl chloride, carbontetrachloride, methyl chloroform, benzyl chloride, ethylbenzyl chloride,chloroethylbenzyl chloride or vinylbenzyl chloride in magnesiumcontainers. In addition the present invention also concerns thepurification of such chlorinated hydrocarbons in magnesium stills.

It is well known that Friedel-Crafts catalysts such as HC]. or AlClcause rapid and sometimes explosive decomposition of many' chlorinatedhydrocarbons such as thosesetforth above. To forestall these undesirabledecompositions these chlorinated hydrocarbons are usually perpared andstored in nickel equipment, and containers, and are 'stabilized by theaddition of chemical stabilizers. Further, the purification is carriedout in glass-line equipment or nickel equipment to prevent degradationof the chemical;

It has now been found that certain magnesium alloys will not react withthese, halogenated hydrocarbons; One can employ an alloy containingaluminum in the amount of 0 to 9 percent by weight and minor amountsless than 6% by weight of manganese, thorium, zinc, or zirconium, thesealloys have'ASTM or SAE numbers as follows:

SAE ASTM Alloy Composition 52 B 107-56'1..- AZBlB (AZ31C)..- 3% Al; 1%Zn; Bal. Mg. 520 B 107-56T.-- AZ6lA 6.5% A]; 1% Zn; B81. Mg. 523 B10756T AZ80A 8. A1; 0.5% Zn; B al. Mg. 522-.." B 107-56T MIA 1.213%; Mn;0.14% Ga; Bal.

The following examples illustrate the present invention but are not tobe construed as limited except by the claims appended hereto:

Apparatus and test methods for collection of storage data of aralkylhalides in magnesium alloy containers Patented Oct. 8, 1968 ice standuntil well separated before use. The wet fluids had a milky appearance.

The test results were obtained by examining the fluids visually and bymeasuring refractive index of the fluids before and after the test andobtain the increase or decrease by difference and, also, by visualexamination of the containers after sawing them in half lengthwise. Inthis way, deterioration of the liquids and/or the containers could beobserved.

The containers were stored in a walk-in hood in which steam wascontinually venting; the atmosphere was consequently quite humid. Thiswould affect the open-container tests.

A summary of performance is given in Table I. It will be observed thatin the three-month test in closed Mg cans, all the fluids exceptvinylbenzylv chloride (VBC) appeared to be little affected, althoughsome color change occurred. The wet VBC has polymerized to a veryviscous syrup, while the dry fluid still was about as fluid as SAE 20oil (the viscosity of the VBC on starting was 1.89 cp. at 25 or aboutthe same as Kerosine).

The condition of the interior of the containers was also observed. Thecans containing the dry liquids were in excellent condition, while thosecontaining wet liquids had all suffered attack to a greater orlesser'degree, the can containing wet chloroethylbenzyl chloride (CEBC)being in the worst condition.

After six months exposure in Mg cans much the same picture waspresented. The liquids, except for VBC were in good condition. The dryVBC had polymerized to a heavy syrup while the wet VBC had become aclear yellow polymer, slowly soluble in toluene.

The Mg containers, after six months, were about like the three-monthones except for a slight haziness after contact with the dry liquids.

Since the above tests are representative of the most severe storageconditions, another three-month test was run using anhydrous fluids andopen containers, at condition which would be representative of a drum inuse with the cap left ofl. Also, as a standard of comparison, the sametest was run simultaneously using nickel containers.

Judging by the refractive indexes in this series of tests, none of theliquids had undergone significant decomposition. The VBC in magnesiumcontainers had an excellent appearance, as did the ethylbenzyl chloride(BBC) in nickel'and VBC in nickel. The BBC in magnesium was turbid butcolorless while the CEBC in magnesium was turbid, light brown and hadsediment present. In the case of CEBC in nickel, the liquid was clearbut dark green, possibly indicating nickel in solution.

The appearance of the interior of the containers was noted. Themagnesium cans all had light specks of corrosion in the vapor space, anda greater or lesser dgeree of corrosion around the upper rim. Except forthe can containing EBC, which had a fairly heavy apple-green deposit inthe liquid space, the nickel cans gave excellent results.

Finally, a severe-condition test was run on closed nickel containers,using water-saturated liquids. In all cases, the liquids after threemonths contained a separate aqueous phase. The indexes suffered littlechange, although the liquids showed turbidity and in two cases, colorchanges.

The nickel cans containing BBC and VBC performed well, with only slightdiscoloration, while the can containing CEBC had heavy red-browndeposits in the liquid space and yellow-brown deposits in the vaporspace.

It was thus demonstrated that magnesium-alloy containers give excellentresults when water was excluded from the system.

TABLE 1 LIQUIDS AFTER STORAGE Test conditions Liquid Additives, 100p.p.m.

Increase or decrease in Color 4 Remarks 6 Mg cans sealed 3 months EBC 1dry t-butyl eatechol EB (TB C)m nitro-pcresol (MNPC) diphenyl amine (DPA).

V Mg cans sealed months. E

Mg cans open 3 months Ni cans open 3 months...

VBC dry--. Ni cans sealed 3 months. EBC wet CEBC wet VBC wet 1EEC-ethylbenzyl chloride, water white; 2 CEBC-chloroethylbenzylchloride, yellow; 3 VB C-vinylbenzyl chloride, yellow;

4 W.W., water White; Dk., dark; Lt., light; Gr., green; Yel., yellow;Br., brown;

5 Tturbid; Sslight sediment observed.

Example 2 The following example illustrates the utility of magnesiumalloys for use in distillation equipment when purifying aralkyl halides.

The alloy of Dowmetal used was AZ31 since this is the most common alloyand is available in a wide variety of shapes, it would be expected to bethe more widely em ployed of the alloys. A column 5 ft. high of 4 OD.Dowmetal, equipped with a glass head and boiling flask was arranged forcontinuous distillation. The column was started up on chlorinatorproduct, which is approximately a :50 mixture of ethylbenzyl chlorideand chloroethylbenzyl chloride. The ethylbenzyl chloride was taken offoverhead. After 143 hours of operation, the still was shut down andrestarted as a flash still, taking chloroethylbenzyl chloride overhead.This operation was continued for an additional 811 hours and finallyshut down when the feed was exhausted. During this run, samples weretaken of the distillate and residue for magnesium analysis. From theresults as shown in Table III it appears that there is an initial slightattack but that the metal becomes deactivated. The interior of thecolumn was very clean after this run.

TABLE IIL-MAGNESIUM CONTENT OF DISTILLATE AND RESIDUE FROM PART-DOWMETALCOLUMN A second column was fabricated almost entirely from DowmetalA231. The reboiler was a thermosyphon type, using a single tube heater.Due to the impossibility of using steam as a heating medium, a 4500 wattDowtherm boiler was used to heat tri-isopropylbenzene, which was thencirculated through the magnesium reboiler at 200 C. Flange fittings withpoly tetrafluoro ethylene envelope asbestos gaskets were used to couplethe iron boiler to the Dowmetal unit. The reboiler was equipped with aballjoint residue take-ofi tube which fitted a glass socket in thereceiver system. A flanged-in thermowell was centered in the heatingzone. The unit was insulated with 1" pipe covering. The overall heightof the reboiler was approximately V.viscous V.viscous Solid Dk. Gr.Aq.phase.

Do. Do.

The column section consisted of the original 5 ft. column, surmounted bya 3 /2 ft. extension, into which was welded a feed tube. This column wasalso packed with /2 Berl saddles.

The still head was composed of a 26 disengaging section, fitted with athermowell and metal ball connection to fit a reflux tube, topped by alength of 2 OD x A wall magnesium alloy AZ31B tubing bent into a turn,with no welds breaking the continuity. The takeoff end was surrounded bya water jacket, giving a condensing area of approximately 113 sq. in. Abrace rod be tween the Water jacket and the disengaging sectionprevented the bend from springing open when heated.

Water saturated with zinc chromate was used as the coolant. To avoidreplenishing the chromate, the coolant was recycled, being in turncooled by a stainless steel shell and tube heat exchanger using tapwater.

To the take-off flange was attached a glass stream-splitter, with amagnetically operated swinging spout. With the magnet deactivated, thedistillate was returned to the column by way of a U-trap and a refluxtube. The other take-off led to a glass receiver system.

The still was operated by charging a feed of vinylbenzyl chloride andchloroethylbenzyl chloride into the still column, heated to 200 C.Periodic samples were taken of the overhead and residue and analyzed formagnesium content. The results of the analysis are set forth below.

TABLE V.MAGNESIUM CONTENT OF DISTILLATE AND RESIDUE FROM COMPLETEDOWMETAL COLUMN Sample description Hours of Percent Mg operation Vinylbenzyl Cl (overhead) 33 0. 0001 ClEt benzyl Cl (residue). 33 0.0007Vinyl benzyl Cl (overhead 101 0.0001 ClEt benzyl Cl (residue) 101 0.0001Vinyl benzyl Cl (overhead). 151 0. 0001 ClEt benzyl Cl (residue)..- 1510. 0001 Vinyl benzyl Cl (overhead) 179 0. 0001 stabilized condition incontainers of magnesium alloy having from 0 to 9% by weight Al, andminor amounts less than 6% by weight of at least one of the metalsthorium, zinc, manganese and zirconium.

2. The method for distilling aralkyl and aliphatic chlorinatedhydrocarbons which undergo decomposition or polymerization in thepresence of aluminum selected from the group consisting of methylchloride, carbon tetrachloride, methyl chloroform, benzyl chloride,ethylbenzyl chloride, chloroethylbenzyl chloride and vinylbenzylchloride, which consists of conducting the distillation in stills ofmagnesium alloy having from 0 to 9% by weight Al, and minor amounts lessthan 6% by weight of at least one of the metals thorium, zinc, manganeseor zirconium.

3. A still for purifying chlorinated hydrocarbons comprising aliquid-vapor zone having a vapor outlet at its top connected by a tubingto a condensing zone which is below the outlet of a reboiler associatedwith said liquid vapor zone to deliver vapor and liquid in a heatedcondition to said vapor-liquid zone, all of said components consistingof magnesium alloy having from 0 to 9% by 6 weight Al, and minor amountsless than 6% by weight of at least one of the metals thorium, zinc,manganese and zirconium.

References Cited UNITED STATES PATENTS 1,932,474 10/1933 Penhaligcn75-168 2,068,868 1/1937 Pier et a1. 196-133 2,314,024 3/1943 Topping75l68 2,870,094 1/ 1959 Cathcart 260-652.5 2,849,430 8/1958 Amos et a1.l5948 2,999,886 9/1961 Crabb et a1 260-6525 3,274,077 9/ 1966 Holfenberget a1 20386 2,079,786 5/1937 Beck 20684 OTHER REFERENCES C. S. Roberts:Magnesium and Its Alloys, pub. 1960, N.Y., pp. 159, 160, 202 and 203,relied upon.

WILBUR L. BASCOMB, JR., Primary Examiner.

